- When a switch is open, no signal is provided to the corresponding input of the ECM. This "no signal" condition is also called "floating".
- When a switch is closed, a ground signal or a +battery signal is provided to the corresponding input of the ECM.
Pressure Switch for the Output Transfer Gear
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| Illustration 1 | g00805530 |
Schematic of the Pressure Switch for the Output Transfer Gear | |
The pressure switch is an input to the ECM. The pressure switch is located in the radiator enclosure behind the cab. The switch is located on the lower left side of the enclosure for the 735 and 740. For the 725 and 730 machines, the switch is located on the lower right side of the machine. The switch is located on the inside of the frame rail on the tractor. The ECM determines if the pressure for the output transfer gear is low and the ECM informs the Caterpillar Monitoring System. The pressure switch connects to the ECM through contacts J1-49 and J1-12. When the pressure of the output transfer gear is low, the switch is open. When the pressure is high, the switch is closed. See Systems Operation, "Tattletale Function" for additional information for the "Low Output Transfer Gear Pressure Event".
Filter Bypass Switch for the Output Transfer Gear
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| Illustration 2 | g00805491 |
Schematic of the Filter Bypass Switch for the Output Transfer Gear | |
The filter bypass switch is an input to the ECM. The bypass switch is located on the housing of the filter for the output transfer gear. The bypass switch is located in the radiator enclosure behind the cab. The bypass switch is located on the lower left side of the enclosure for the 735 and 740. For the 725 and 730 machines, the bypass switch is located on the lower right side of the machine. The switch is located on the inside of the frame rail on the tractor. The bypass valve will open in order to protect the system if the filter is restricted. The bypass switch provides an input signal to the ECM. The ECM will determine if the filter is restricted and the ECM will inform the Caterpillar Monitoring System. The filter bypass switch connects to the ECM through contacts J1-60 and J1-12. See Systems Operation, "Tattletale Function" for additional information for the "Output Transfer Gear Filter Plugged Event" and "Low Output Transfer Gear Pressure Event".
Temperature Switch for the Output Transfer Gear
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| Illustration 3 | g00805531 |
Schematic of the Temperature Switch for the Output Transfer Gear | |
The temperature switch is an input to the ECM. The temperature switch is located in the radiator enclosure behind the cab. The temperature switch is located on the lower left side of the enclosure for the 735 and 740. For the 725 and 730 machines, the temperature switch is located on the lower right side of the machine. The switch is located on the inside of the frame rail on the tractor. The ECM will determine if the temperature of the output transfer gear is low. The ECM uses the information in order to determine the filter and the pressure events. The temperature switch connects to the ECM through contacts J1-50 and J1-12. When the temperature of the output transfer gear is below the threshold, the switch is closed. When the temperature is above the threshold, the switch is open. See Systems Operation, "Tattletale Function" for additional information for the "Output Transfer Gear Filter Plugged Event". See Systems Operation, "Tattletale Function" for additional information for the "Low Output Transfer Gear Pressure Event".
Transmission Oil Filter Bypass Switch
(S/N: AGFAWRAFX)
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| Illustration 4 | g00586096 |
Filter Bypass Switch | |
The filter bypass switch is an input to the ECM. The bypass switch is located on the housing of the transmission control filter. The bypass valve will open in order to protect the system if the filter is restricted. The bypass switch provides an input signal to the ECM. The ECM determines if the filter is restricted and the ECM informs the Caterpillar Monitoring System. The filter bypass switch connects to the ECM through contacts J1-12 and J1-54. See Systems Operation, "Tattletale Function". View the event for the "Transmission Filter Plugged Event" for additional information.
Service Brake Pressure Switch
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| Illustration 5 | g00381992 |
Service Brake Pressure Switch | |
The service brake pressure switch is an input of the ECM. The switch connects to contact J1-46. The switch tells the ECM when the brake control valve is active. The operator activates the brake control valve with the brake pedal. The ECM initiates the elevated shift function. The ECM then cancels the bidirectional shift function. The switch is located on the foot operated brake control valve in front of the cab. The switch is open during normal machine operation. The brake control valve is not active. The switch closes to ground when the brake control valve is made active by the operator.
The switch has two contacts in the harness connector. One of the connector contacts is connected to the ECM. The second connector contact is connected to J1-12. The switch is normally open.
The ECM records diagnostic codes with the service brake signal as a CID 0704. A record of the diagnostic code is made while the machine is in operation.
Parking Brake Switch
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| Illustration 6 | g00382132 |
Parking Brake Switch | |
The parking brake switch is an input of the ECM. The parking brake switch connects to connector contact J1-44. The switch tells the ECM that the operator wants to activate the parking brake. The operator activates the switch by pulling on the parking brake knob. The ECM activates the parking brake by activating a solenoid driver. The solenoid driver de-energizes the parking brake solenoid. The parking brake is now engaged.
See Testing and Adjusting, "Parking Brake Function" for more information on the operation of the park brake. When the ECM initiates the parking brake function, the ECM cancels the bidirectional shift function. See Testing and Adjusting, "Elevated Downshift Function" for more information.
The switch and the knob are located on the dash panel in the cab. The switch is closed to ground when the parking brake is pushed in by the operator and the parking brake is OFF. The switch opens when the parking brake knob is pulled out by the operator and the parking brake is ON (engaged).
The switch has four contacts in the harness connector. Contact 1 connects to the ECM. Contact 2 connects to J1-12. Contacts 3 and 4 are not used.
The ECM does not record diagnostic codes that occur with the park brake switch.
Differential Lock Switch
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| Illustration 7 | g00384844 |
Differential Lock Switch | |
The differential lock switch is an input to the ECM. The differential lock switch connects to connector contact J2-30. The switch tells the ECM that the operator wants to activate the differential lock. The ECM checks for certain conditions and parameters. The ECM then determines if the differential lock should be activated. The switch is located on the floor of the operator compartment.
The differential lock switch has two contacts in the harness connector. One of the connector contacts is connected to the ECM. The other connector contact is connected to +battery power. The differential lock switch is a momentary switch that is normally open.
The ECM does not record diagnostic codes that occur with the differential lock switch.
Selector Switch (Cross Axle Lock)
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| Illustration 8 | g00518764 |
Schematic of the Selector Switch for the Cross Axle Lock | |
The selector switch for the cross axle lock is an input of the ECM. The switch connects to connector contact J1-11. Ground is at J1-12. The switch tells the ECM that the operator wants to enable the solenoids of the cross axle lock. The operator activates the switch by toggling the rocker switch.
When the selector switch for the cross axle lock is ON, the switch is closed. When the selector switch for the cross axle lock is OFF, the switch is open.
See Systems Operation, "Differential Lock Function" for additional information on the function of this switch.
The ECM does not record diagnostic codes that occur with the switch of the cross axle lock.
Parking Brake Pressure Switch
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| Illustration 9 | g00518275 |
Parking Brake Pressure Switch | |
The parking brake pressure switch is an input of the ECM. The switch connects to connector contact J1-45. The switch tells the ECM when the parking brake is engaged. Connector contact 1 connects to the ECM J1-12 ground. Connector contact 2 connects to the ECM J2-26. Connector contact 3 is not used. When the parking brake is disengaged, connector contact 2 is closed. When connector contact 2 is open, the parking brake is engaged.
The ECM records diagnostic codes with the parking brake as a CID 0627. A record of the diagnostic code is made while the machine is in operation.
Key Start Switch
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| Illustration 10 | g00291705 |
Key Start Switch | |
The key start switch is an input of the ECM. The switch connects to connector contact J1-40. The switch tells the ECM that the operator wants to start the engine. The ECM then initiates the neutral start function. See Systems Operation, "Neutral Start Function" for more information. The signal is open during normal operation. When the key start switch is in the START position, the switch will close to the +battery circuit.
The switch has four terminals. Terminal "S" connects to the ECM. Terminal "B" connects to battery voltage. Terminal "C" connects to the engine shutdown control. Terminal "R" connects to the main relay.
Note: After the switch is initially turned to the START position, the switch will not return to the START position from the ON position. The switch must be turned to the OFF position. The switch can then be turned to the START position.
The ECM does not record diagnostic codes that occur with the key start switch.
Retarder Lever
(S/N: AGFAFX)
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| Illustration 11 | g00805529 |
Schematic of the Retarder Lever | |
| Circuit Continuity | ||||
| Retarder Lever Switch | ||||
| Lever Position | Connector Contact (2) of the Switch | Connector Contact (3) of the Switch | Connector Contact (4) of the Switch | |
| 1 | Off | Open (1) | Open | Open |
| 2 | Low | Open | Open | Closed (2) |
| 3 | Med | Closed | Open | Closed |
| 4 | High | Open | Closed | Closed |
| ( 1 ) | Open Circuit |
| ( 2 ) | Circuit Continuity |
The retarder lever is an input to the ECM. The retarder lever connects to the ECM through connector contacts J1-55, J1-56, and J1-57. The retarder lever connects to ground at J1-12. The retarder lever tells the ECM the desired setting for the retarder. The retarder has four positions. The OFF position, the LOW position, the MEDIUM position and the HIGH position. Table 1 shows the state of the contacts in each of the positions. See Systems Operation, "Retarder Function" for additional information on the function of the retarder lever.
Switch (Top Drive Gear)
The switch is an input to the ECM. The switch connects to the ECM through connector contact J1-47. Ground is at J1-12. The switch limits the highest gear that is engaged by the transmission. The ECM then restricts the transmission from shifting past the indicated top gear.
The switch is located on the shift lever. The switch is located under the operator's thumb.
The gear positions for the gear selector are listed:
- First
- Second
- Third
- Drive
- Neutral
- Reverse
The drive position on the gear selector is used in order to select the gears from the fourth gear to the top gear.
When the gear selector is in the drive position, the operator uses the top drive gear switch in order to select the desired setting of the gear selector. Before the drive gear decreases, the top drive gear is activated for 5.0 seconds.
The drive gear is held to the current value for 2.5 seconds before the drive gear will decrease again. When the fourth gear is reached by the drive gear, the drive gear will return to the maximum gear. If the switch for drive is released, the current value of the drive gear is held.
When the drive gear changes, the gear is shown on the actual gear indicator display of the Caterpillar Monitoring System.
The Caterpillar Monitoring System will indicate the selector switch by flashing the current setting at a 2.0 Hz rate. After the drive gear has been selected, the display for the Caterpillar Monitoring System will return to the actual gear and the display will stop flashing.
The setting for the top drive gear is lost when the control is turned off. When the control is powered up, the top drive gear is set to the maximum gear. The top drive gear will remain set to the maximum gear until the operator changes the setting.
Hold Toggle Switch
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| Illustration 12 | g00805796 |
The hold toggle switch is an input to the ECM. The hold toggle switch connects to the ECM through connector contact J1-19. Ground is at J1-15. The hold toggle switch tells the ECM that the operator wants the transmission to stay in the current gear. The ECM then places the transmission on hold.
The switch is located on the shift lever. The switch is under the operator's thumb. This switch is a momentary switch. The operator activates the switch by pressing the switch and then releasing the switch. When the switch is operated the value of the hold function is changed to a new value.
Steering Pressure Switch
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| Illustration 13 | g00385532 |
Steering Pressure Switch | |
The steering pressure switch is an input of the ECM. The switch connects to the contact J1-27. The switch tells the ECM the primary steering pressure. When the steering pressure is low the ECM will activate the secondary steering pump.
The switch has a normally open contact and a normally closed contact. One side of the normally open contact is connected to the ECM. The other side is connected to ground through the ECM. The last connector contact of the switch is not used. The switch is normally open.
The ECM does not record diagnostic codes that occur with the steering pressure switch.